1. Field of the Invention
The present invention relates to a circuit connected to an AC power supply, and a heating apparatus using the circuit.
2. Description of the Related Art
Conventionally, a circuit which is connected to an AC power supply and cuts off an overcurrent from it using a fuse is known. In Japanese Patent Laid-Open No. 7-231659, a fuse is arranged on one of the two supply lines of a commercial AC power supply and blown out when an overcurrent flows to the supply line of the power supply. The fuse is also blown out by forcibly increasing the load current upon detecting an abnormality in the circuit.
However, even when the fuse has cut the current in only one supply line of the commercial AC power supply, as described above, an impedance that exists between the ground and the commercial power supply causes an unnecessary current to continuously flow from the other supply line without a fuse.
A typical situation will be described with reference to FIG. 7. When a fuse 4 is blown out by, for example, a short in a load circuit 11, an unwanted current Ic from a commercial AC power supply 1 continuously flows to ground 10 via a noise removing coil 7 and a noise removing capacitor 9.